Combined physical color and subjective color



June 2, 1970 J. E. BUTTERFIELD COMBINED PHYSICAL COLOR'AND SUBJECTIVECOLOR Filed March 24, 1967 6 Sheets-Sheet 2 I Ib Y Junez, 197() F.BOTTERFIELD I 3,515,492

COMBINED PHYSICAL COLOR AND SUBJECTIVE COLOR Filed March 24, 1967 6Sheets-Sheet 3 .....m W f'f A BY June 2,'1970y J. F. B'u'rTERr-'IELDCOMBINED PHYSICAL COLOR AND SUBJECTIVE COLOR Filed March`24, 1967 6Sheets-Sheet 4 June 2, 1970 J. F.BTTE'RF|ELD y 3,515,492

COMBINED PHYSICAL COLOR AND SUBJEOTIVE COLOR Filed March 24, 1967 v -K esheets-sheet s /p//ASS PUTS OUT M qnmsf ONLY I gi-'156 JM/,CS T//Z/' lINVENTOR.

June 2, 1970 J. FQ laUTTL-:RFIezLD 3,515,492

COMBINED PHYSICAL' COLOR AND SUBJECTIVE COLOR l Filed March 24, 1967 vessheets-sheet e 'United States. Patent Office 3,515,492 Patented June 2,-1970 3,515,492 COMBINED PHYSICAL COLOR AND SUBJECTIVE COLOR .lames F.Butterfield, Van Nuys, Calif., assignor to The Battelle DevelopmentCorporation, Columbus, Ohio, a

corporation of Delaware Filed Mar. 24, 1967, Ser. No. 625,813 Int. Cl.G09f 19/12, 13/34 U.S. Cl. 356-256 Claims ABSTRACT OF THE DSCLOSURE'Physical color and subjective color may be combined to provide mixedcolor or saturated color. This may be accomplished by modulating lighteminating from a physical color in accordance With a subjective colorcode, such as by modulating a physical color light source in accordancewith a `subjective color code, and if the code is one for producing asubjective color of the same hue as the physical color the result willbe highly saturated color. These concepts may be used in conjunctionwith color television, lasers, signal lights, displays, and the like.Also disclosed is the modulation orf a light source with a complex codeto provide subjective color.

Reference is made to applicants copending application Ser. No. 307,976,filed Sept. 10, 1963, and entitled Subjective Color System, now Pat. No.3,311,699 and to applicants copending application Ser. No. 625,783 ledconcurrently herewith and entitled Production of Subjective Color byAnimation Techniques, the disclosures of which are incorporated hereinby reference.

This invention relates to methods and apparatus for combining physicalcolor and subjective color and for obtaining higher saturations ofcolor.

By physical color, it is meant the color that one is normally acquaintedwith such as the blue of the sky, the red of a stop light and the greenof the grass. These are objects which either refract, produce or reflectcertain wavelengths of light. When this physical colored light fallsonthe receptors (cones) of the eyes, it causes a signal to be sent overthe optic nerve to the `cortex of the brain. The receptors apparentlyare able to determine the specific Wavelength ott lthe light falling onthem and they generate an apprporiate coded signal for transmission viathe optic nerve. The cortex identities the signal as having the code fora particular color of light.

The greater percentage there is of a particular wavelength of lightfalling on a specific group of the receptors of the eye, the greater thecolor saturation of that particular source of color. If some white, orother hues of light, are mixed with the particular colored light, thesaturation is decreased. However, if the light is nearly all of oneparticular wavelength, the saturation is Very high and theoretically ifall the light were of a particular Wavelength, the saturation would beone-hundred percent. In nature, highly saturated objects or sources oflight are unusual. Highly saturated artificial lights are usually dimbecause of the low transmission of the narrow band filters required, andlarge amounts of energy are `required to obtain'a reasonable amount oflight. An exception is the laser which may be highly monochromatic,i.e., saturated in one color, but lasers have a number of limitations'which limit their use.

There has been investigation and observation of the subjective colorphenomenon over the years. Benedict Prevost is credited with discoveringthis phenomenon in the early eighteen hundreds. ISubsequently, J. R.Fechner experimented with black and white rotating discs. Approximatelyhalf a century later C. E. Benham designed a dise having only black andwhite patterns thereon, some of which would appear in color when thedisc was rotated. The repetition of certain sequences of light and darkareas apparently is interpreted by the eye and brain as color, and thecomposition of the sequence and rateV of repetition determine thecharacteristics of the color. U.S. Pat. No. 2,844,990 to Nagler et al.described production of subjective color by presenting a seriesofpictures with motion picture or television equipment. This isaccomplished by preparing individual film frames wherein the areas toappear in subjective color are formed by a plurality of spaced black andwhite lines or cross hatching.

In Pat. No. 3,311,699 noted above, there are disclosed for producingsubjective colors several methods and arrangements of making areas orcolor components appear light and dark in certain sequences rather thanby using spaced lines or cross hatching as disclosed by Nagler et al.According to said patent, live pickup of a scene or image may beaccomplished through the use of filter means in conjunction with atelevision or motion picture camera. Said corresponding applicationentitled Production of Subjective Color by Animation Techniques relatesprincipally to the production of selected subjective colors in arelatively simple manner through the use of animation techniques.

It is the primary object of this invention to provide a method andapparatus for combining physical color and subjective color to therebyobtain saturations of color higher than is normally possible with eitherphysical color or subjective color alone.

Another object of this invention is to obtain saturations from a givensource of color which are higher than the source normally providesWithout requiring a corresponding incease in the total energy output ofthe source, and without a signilicant increase in the energy input,

A further object of this invention is to enable signal lights(navigation, railroad, traic, space, under water, surface, airline,etc.) to be more saturated and therefore perceivable against abackgrounud of illumination noise over greater distances than normallyis possible.

Another object of this invention is to add subjective color toilluminated and other advertising displays in a manner to enable certainof the illuminated parts to appear in highly saturated hues periodicallyor conv tinually.

Still another object of this invention is to combine physical color withsubjective color in the pickup, transmission or reception of television,motion pictures or other types of communication or displays. This isparticularly useful in the production of subjective color on televisionequipment, such as described in said Patent No..

3,311,699 wherein the color produced is not highly. saturated. Thecombination of physical color with less -saturated subjective colorprovides pictures of high saturations. This also stabilizes thesubjective colors, makes them uniform through the colored area and canreduce flicker.

Furthermore, it is an object of the invention to enable the addition ofsubjective color to the entire image, or to certain areas of the image,in physical color communication systems (for example, NTSC colortelevision, color motion pictures, etc.) to thereby emphasize all orcertain areas of the picture or obtain colors or saturations notnormally available with the particular' other sources where only onenarrow band hue is possiblek from a particular source while yet anotherhue is required for a particular use.

In the subjective color literature and in recent tests, it has beendetermined that many color-blind individuals can see subjective colorsof hues to which they are normally blind. For example, a protanope maynot normally see physical red probably because his physical redreception mechanisms are defective. However, he may see subjective redbecause the remainder of his color identifying mechanism is intact.Subjective` color bypasses the physical color mechanism of the receptorssending a signal to the cortex similar to that which the receptor mighthave sent. Therefore, -a further purpose of this invention is tosubjectively code physical color lighting so that many who arecolor-blind can identify its color. This is particularly applicable tosignal lights.

Briey, these and many other objects and advantages of this invention`are attained by combining physical color and subjective color. Thepoint of combination may be at the actual source of either the physicalor subjective color, at some point in Ibetween, or at the eye.

For example, a source of physical color such as a red stoplight may bemodulated Iwith the subjective color code for red. This involvesilashing the red light in a particular manner. One method involvesadding a white surround around the red area and ashing the whitesurround and the red area olf and on in a particular manner. Anothermethod is to only ilash the red area in a more complex manner. It may beassumed that the normal saturation of the physical red color is sixty-vepercent. It also may be assumed that if there were merely a white lightashing to give a subjective color stimuli of red, the saturation of thesubjective red color stimuli would be twenty-five percent. Now, when thephysically colored red stoplight is modulated with the subjective redcode of approximately the same wavelength of red, then the stoplight isperceived at a higher saturation than it would be normally. Thissaturation appears to be almost a simple summation of the two, that is,ninety percent. Whether the saturation could reach or be more than thetheoretical one-hundred percent is still not clear. Another usefulexample is modulation of physical red laser light with the subjectivegreen code thereby producing yellow light which may be desired for aparticular purpose.

Another particularly useful application is in color television. Forexample, the physical blue colored word new in the production of a colortelevision commercial may be modulated with the subjective code for blueso that this word -appears more saturated on a color set than thephosphors of the color tube are normally capable of producing. Anotherapplication is to selectively add subjective color to physical coloreddisplays of various kinds, e.g., radar, command, sonar, teachingmachines, and so forth, so that certain areas of information can beemphasized or treated specially.

These and other objects and features of the present invention willbecome apparent through a consideration of the following descriptiontaken in conjunction with the drawings in which:

FIG. 1A illustrates a Benham-type disc useful in explaining the additionof subjective color and physical color;

FIG. 1B illustrates another configuration of Benhamtype disc;

FIG. 2 illustrates a Benham-type disc illuminated by a physical coloredlamp;

FIG. 3 is a perspective view illustrating a `Bidwell-type disc used withan advertising display;

FIG. 4A is a perspective view of a bank of signal lamps, wherein theprinciple of combining subjective and physical colors is illustrated;

FIG. 4B is a cutaway side view of one of the signal lamps of FIG. 4A;

FIG. 4C is a graph showing the voltage cycles used in causing the lampof FIG. 4B to appear in various subjective colors;

FIG. 4D is a cutaway side view of another of the lamps of FIG. 4A;

FIG. 4E is a graph of the voltage cycles used in causing the lamp ofFIG. 4D to appear in highly saturated colors;

FIG. `4F is a cutaway side view of another of the lamps of FIG. 4A;

FIG. 4G is a graph of the voltage variations used in causing the lamp ofFIG. 4F to appear in highly saturated colors;

FIG. 5A is a perspective view of a signal light in which a modifiedBidwell-type disc is utilized;

FIG. 5B is a cutaway side view of the signal light of FIG. 5A;

FIG. 5C is a front View of the signal light of FIG. 5A;

FIG. 6A is a perspective view of a signal light using slide projectorsand a Bidwell-effect disc;

FIG. 6B illustrates three slides used in the slide projectors of FIG.6A;

FIG. 6C illustrates diagrammatically the phase sequence used in thesignal light of FIG. 6A;

FIG. 7A illustrates a configuration of a signal light in which a drum ofneutral density lters and masks is employed;

FIG. 7B illustrates the neutral density value of the various sectors ofthe drum used in FIG. 7A;

FIG. 8A is a perspective view of an advertising display;

FIG. 8B is a cutaway side view of the advertising billboard of FIG. 8A;

FIG. 8C illustrates the various phases of the advertising display ofFIG. SA;

FIG. 9 is a perspective view of a command room display utilizing slideprojectors with computer controlled shutter mechanisms;

FIG. 10A ilustrates an example of the phases used` when combiningsubjective color and physical color on color television or color motionpicture film; and

FIG. 10B illustrates the resulting reproduction of the scene of FIG.10A.

Referring now to the drawings, FIG. 1A illustrates a typical Benham-typedisc which is rotated in a clockwise direction at 3.5 to 20 revolutionsper second (r.p.s.). The disc consists of black opaque sector 1 andwhite sector 2. White sector 2 has three arc segment lines; a redcreating line 3, a green creating line 4, and a blue creating line 5.The white arc segment 6 immediately follows line 3, and isindistinguishable from white sector 2.

These lines in a Benham disc are black when the disc is stationary. Whenthe disc is rotating clockwise, the Inner line 3 appears as a reddishblur circle, the middle line 4 appears as a greenish blur circle, andthe outer line 5 appears as a bluish blur circle. The exact subjectivecolor of each line can be determined by comparing it to a color system,such as the color chips in the Munsell Book of Colors, in accordancewith the teachings in said above application entitled Production ofSubjective Color by Animation Techniques. Assume, for example, that thesubjective red color of line 3 can be designated by Munsell Notation 5.0R 5/10, the subjective green of line 4 can be designated 5.0 G S/4, andthe subjective blue of line 5 can be designated 7.5 PB 3/10.

Now assume that in FIG. 1A there is illustrated a Benham-type disc whichhas arc lines 3, 4 and 5 physically colored (paint, ink or othermaterial may be employed) according to the Munsell notation. That is,line 3 `may be made from 5.0 R 5/10` Munsell paper, line `4 made from5.0 G 5/4 paper, and line 5 made from 7.5 PB 3/ 10 paper. In otherwords, lines 3, 4, and 5 have been made of physically colored paper ofthe exact same shade that they will appear in subjective color. Inactual practice the color hue and value are maintained, but highersaturations of physical color are used since they are easier to obtain.

When the disc in FIG. 1A is revolving clockwise, the line 3 appears abright red, the line 4 appears a bright green, and the line 5 appears abright blue. The saturation (chroma) in each case is greater than thesaturation of the colored paper alone (when the disc is stationary). Thesaturation of the colored lines when the disc is revolving is asummation of the saturation of the subjective color and the saturationof the physical color. Also, the values (brilliancy) of the colorsappear greater.

A substantiative demonstration of the combination of subjective colorand physical color can be made by reversing the direction of rotation ofthe disc. Counterclockwise rotation results in line 3 creating asubjective blue which adds to the physical red color of the line to makeit appear a magenta. Line 4 remains a bright green because it stillappears as a combination of subjective green and physical greenregardless of the direction of rotation. Line S appears magenta becausenow it creates a subjective red which is combined with the physical bluecolor of the Munsell paper. The magenta colors of lines 3 and 5 will benearly identical if the subjective and physical colors are well matched.

Therefore, the combination of subjective and physical color is additive;however, when different hues are combined a mixed color results. Forhighest saturations care must be taken in selecting subjective andphysical colors of exactly the same hue or the result will be a mixedcolor of only medium saturation.

A further interesting case is the combination of two complementarycolors on a white background. For example, the physical color cyan canbe combined with subjective red. The result is a white color whichblends in and disappears into the white background.

A further interesting cause is to use, for the physical color,fluorescent paper, which appears highly saturated. The combination ofthe fluorescent effect, physical color and subjective color is brilliantand very highly saturated.

The additive effect is more notable With blues and reds and less so withyellows and greens. This seems to occur because physical blues and redsare most highly saturated when they are of lower color value (darker,that is, containing less white). The darker the physical color, thegreater the subjective color effect. For example, if line 4 were lightgray, it would not be as saturated a subjective color as if it were darkgray or black. Physical colored yellows and green are most highlysaturated when they are of higher color values (lighter, i.e.,containing more white), but the subjective color effect is not aspronounced with these colors. To compensate for this, physical coloredyellows and greens should be selected with lower color values (darker)than normal when they are combined with subjective hues.

At these slow speeds (3.5 to 20 r.p.s.), there is a White flashoccurring in saturated lines 3, 4 and 5. This is an undesirable effectand causes each line to have less average saturation because it isphysically and/or subjectively colored l/6 of a cycle and is White 2/6of a cycle; the remaining 3/ 6 of the cycle is black.

However, if the disc in FIG. lA is spun at high speed, for example, 20r.p.s. and above, the subjective color effect will be almost nonexistentand the lines will appear only in physical color. Then, the physicalcolor will be considerably less saturated. This results, in the case ofred for example, because the disc is turning fast enough for the whitearc segment 6 to mix with the physical red color of the line 3 andresult in a desaturated physical red color. Black sector 1 has no effecton this desaturation. The same effect occurs with green and blue. Alsoblack sector 1 causes considerable flicker at slow speed whichdisappears at high speed.

FIG. 1B shows another Benham-type disc illustrating two methods forextending the physical colored areas so as to obtain a better ratio ofphysical color to white arc areas (such as 6), and thereby toproportionately reduce the white flash and increase the total physicalcolor saturation. This in turn provides higher saturation from thecombined physical and subjective colors.

AS in FIG. lB, arc segment 7 is the subjective red creating line and iscomposed of a piece of red paper. Arc segment 8 is the subjective greencreating line and is composed of a piece of green paper. Arc segment 9is a subjective blue creating line and is composed of a piece of bluepaper. Note that line 8 has been extended to encompass twice the angularlength of line 4 in FIG. 1A. This creates a better subjective green andincreases the ratio of physical green to physical white thereby reducingthe white flash. Also, lines 7, 8 and 9 can be made somewhat longer ifthe speed of rotation is increased. Their duration is thereby maintainedwhereas the white arc areas (such as 6) are reduced in duration andcause less white flash at slow speeds or desaturation at high speeds.

In FIG. lB sectors 10 and 11 replace sector 1 of FIG. lA which wasblack. Sector 10 is a physical blue color and sector 11 is a physicalred color in our example. These can be made of Munsell papers 7.5 PB3/10 and 5.0 R 5/10, respectively. When the disc turns clockwise, sector10 follows line 9 extending the durations of physical blue, and sector11 of the disc precedes line 7 extending the duration of the physicalred. Sectors 10 and .11 are presented to the eye at a speed (5 or morer.p.s.) fast enough for them to blend into a magentish gray-white colorwhich causes less flicker than black sector 1 of FIG. lA. Also, theflicker (white flash) in lines 7 and 9 is less because their duration islonger.

Another method of combining physical color and subjective color is touse colored lights for the physical color. FIG. 2 illustratesBenham-type disc 12 with black sector 13, white sector 14 and black arcsegment line 15, which creates subjective red when the disc is rotatedclockwise. Flood lamp 16 illuminates disc 12 with physical red light. Itis assumed, as with FIGS. lA and 1B, that disc 12 is also illuminated byambient white light. When disc 12 is stationary, some of the red lightis seen in arc 15 and sector 13 and they appear a dim physical redcolor. White sector 14 continues to appear white despite the physicalred light falling on it because the eye and brain select it as thereference white. When disc 12 is turning, the physical red lightcombines with the subjective red created by line 15 and causes a moresaturated red to appear in line 15. Likewise a physical green or bluelight can be combined with subjective green or subjective bluerespectively to make them appear more highly saturated. This method isnot very eflicient because black arc line 15 absorbs a high percentageof light.

An alternate method is to direct physical red lamp 16 at the eye and thediffusion of red light across the retina causes the black areas toappear red. Another method is to direct lamp 16 at a semi-rellectingsurface 16a between the eye and disc 12 and view the combined image ofdisc 12 and the physical red light rellected thereon.

A method of combining subjective and physical colors by a Bidwell-typedisc is shown in FIG. 3. Here disc A17 l rotates in front of a display18. Disc y17 has a black sector 19, a white sector 20 and a transparentsector 21 through which display 18 is viewed. Display 18 has whitebackground 22, upon which appears image 23 which is the word SOAP inphysical red color. It will be apparent that the image 23 can be atrademark, design, ad text, etc. The image may be created by red paint,red ink or red material, or it may be red lighting, such as neon tubes.White background 22 corresponds to the white areas 14 on each side ofline 15 in FIG. 2; and image 23 corresponds to line 15. The disc 17 andthe display 18 are illuminated with white light Kso that the whitesector 20 and the white background 22 are about the same intensity ofillumination. When disc 17 is spun slowly clockwise, image 23 appears asubjective red. This subjective red combines with its physical red colorto make image 23 appear more saturated than either its subjective orphysical colors alone.

FIG. 4A illustrates a bank of signal lamps in a housing 30. Each lampconsists of a back illuminated translucent screen(s). A screen 24A isilluminated by a white light 24B (FIG. 4D) and a physical red light 24C.Screens 25A, 26A and 27A are rear illuminated by white lights andphysical colored lights (these latter lights are not shown forsimplicity of illustration). Screens 28A and 29A are illuminated byphysical white lights 28B and 29B respectively (FIGS. 4F and 4B). Screen31A is illuminated by a white light 31B. Screen 32A is illuminated by awhite light 32B (FIG. 4D). Screen 33A is illuminated byfa white light(not illustrated). Screen 34A is illuminated by a white light (notshown), and screens 35A are illuminated by a ywhite light (not shownFIG. 4B shows a cutaway side View of one of the lamp housings 30A. Whitelight 31B is connected through switch 31C to the power main. Light 29Bis connected through switch 29C to the power main. Switches 31C and 29Coperate in synchronism. All switches herein are illustrated only indiagrammatical form and each mechanism can be mechanical or electronic.Although the xed contacts of the switches are shown only as circles thisis done for simplifying illustration thereof, and in actual practicethese contacts are longer (such as arcuate) so that the space betweenfixed contacts is relatively small.

FIG. 4C illustrates graphically on-off voltage cycle sequences and theirduration in milliseconds of white lights 29B and 31B. These voltagecycles are required for screen 29A to appear respectively subjectivered, or subjective green, or subjective blue, or subjective magenta incolor, and are generated by various configurations of switch 29C (whichis shown for the generation of subjective red). To obtain magenta, thevoltage of lamp 29B is turned on partially, then fully, then partially.In each case, screen 31A appears white. Screens 29A and 31A have a slowicker. Subjective color alone, as is created in this manner, is notsaturated.

In FIG. 4D lamp housing 30B is shown in a cutaway side View. Switches32C, 24D and 24E are connected respectively to white light 32B, whitelight 24B and physical red light 24C.

|When the red voltage cycle sequences of FIG. 4E are applied by switches32C, 24D and 24E (shown for the generation of saturated red) to lights32B, 24B and 24C of FIG. 4D, screen 24A appears a saturated red. If thelight 24C is a physical green and the green voltage cycles of FIG. 4Eare applied to the light 24C, white light 24B and white light 32B, thenscreen 24A will appear a saturated green. If the light 24C is a physicalblue and the blue voltage cycles are applied to the light 24C, whitelight 24B and white light 32B, then screen 24A lwill appear a saturatedblue. If the light 24C is a physical magenta and the magenta voltagecycles are applied to the light 24C, white lamp 24B and white lamp 32B,then screen 24A will appear a saturated magenta. If green voltage cyclesof FIG. 4E are applied to physical red light 24C, white light 24B andwhite light 32B, then screen 24A will appear yellow. In FIG. 4A thephysical colored lights must be of a higher wattage than the whitelights so that the illumination output of all lights is about the same.

In FIG; 4A, it is assumed that all lights are of a type which can beturned ON and `OFF within brief periods, which in these examples aretimes per second. Incandescent lights cannot normally be turned ON orOFF at these speeds. However, in some cases, an incandescent lamp can bemaintainedat a low level of illumination so that during the OFF periodsit is actually on very dimly and during the ON periods it is on verybrightly.

Then more rapid fluctuation of the filament temperature is possible.Fluorescent lights and electric discharge lights (such as neon, sodium,mercury, etc.) can Ibe turned ON and OFF at high speeds and areparticularly useful for this purpose. With some of these types of lightsthere is also the requirement of maintaining a constant low basevoltage.

Some subjective color elect and therefore added saturation is achievedif the physical red colored light 24C is maintained ON 4continuously andonly light 32B is turned ON and OFF. In fact, any physical colored lightwill have an enhanced saturation if an adjoining light is turned ON andOFF with corresponding voltage cycles.

FIG. 4F is a cutaway view of housing 36. Here is` shown white light 28Band reflector and translucent screen 28A and switch 37. This arrangementdoes not include the white surround created in FIG. 4B by translucentscreen 31A and light 31B. In this case the entire screen 28A appears incolor. However, the modulation voltage is more complex in nature. TheBenham-type of subjective color is apparently produced by the ON-OFFcycles of the high contrast (black and white areas) acting across acommon border. For example in FIG. 1A a subjective red color is createdin the black area of line 3 when this interacts against the white area 2located on each side of it and the white arc 6 succeeding it. The largedark area 1 is a discharge area and serves to discharge the eyesreceptors before another code sequence is sent. It line 3 is thin, thesubjective red color from the edges spreads across its entire width.However, if line 3 is thick the subjective red color will only be seenat the edges and the center area thereof will appear black. The highcontrast interaction seems to cause a red coded signal to arise onlyfrom those immediate areas of the eye lwhere the interaction takesplace. The subjective color effect illustrated in FIGS. 4F and 4G is ofa dierent nature. Here a complex modulation of light signals inincrements from full OFF to full ON apparently causes the entire area ofthe eye to create a color signal. Where in the lirst case of the highcontrast interaction a limited area caused a color coded signal to besent from the eyes receptors to the brain, now in the later case acomplex modulation of a light signal over any sized area causes a colorcoded signal to be sent from those receptors to the brain. In each casethere is a unique modulation of the light signal termed a subjectivecolored code, which determines the character of the color seen.

FIG. 4G illustrates an example of the complex voltage cycle sequencesrequired respectively for subjective red, subjective green or subjectiveblue, with the x axes being time and the y axes being voltage whichdetermines light intensity from olf to full on. The OFF period isconsiderably reduced. This permits more sequences per second (in thisexample, ten r.p.s.) and considerably reduces the flicker. The voltagecycles are illustrated in digital form but they preferably should beanalog in nature. The various voltage magnitudes may be provided bysuitable valued resistors coupled with the switch 37. In this case,light 28B needs to be capable of very rapid changes in intensity.Instead of utilizing white light 28B, appropriate colored light could beused thereby providing higher color saturations.

Signal arrangements as illustrated in FIG. 4A normally have a circularconfiguration as seen at 24A. However, the Benham-type of subjectivecolor appears to be an edge effect which in FIG. 1A occurs between lines3, 4 or 5, and the white portion of section 2 which lies on each side ofthese lines. It has been determined that the longer the edge between thesurround and the line per unit area, the greater the subjective color inthis area. Also thick lines tend to have good color at their edges anddarker colors or black in their center, therefore thinner lines aredesirable.

In FIG. 4B, screen 29A corresponds to lines 3, 4 or 5 of FIG. 1 andscreen 31A corresponds to white sector 2 of FIG. 1. However, screen 29Ais circular in shape and 'has the minimum possible edge or border.Screen A in FIG. 4A has been made square in shape and has a greaterborder. Screen 26A has a flower-like shape and has considerable border.Screen 27A is ring-like in shape; its center hole is part of screen A.Screen 27A, therefore, has an inner and outer Iborder which assures allareas of screen 27A are close to a border. Screen 28A operates on adiiierent principle of subjective color as described above (col. 8,lines 35 through 62). The entire area creates subjective color without aborder being present.

FIGS. 5A through 5C illustrate another type of signal lamp. Housingcontains a modified Bidwell-type disc 41. This disc consists of opaqueblack sector 42, opaque white sector 43 and translucent screen sector44. Disc 41 corresponds in nature to disc 17 of FIG. 3. Disc 41 isdriven by means of driver wheel 45 and motor 46. Idlers 47 and 48support disc 41. Disc 41 turns clockwise at a speed of approximately 5r.p.s. Translucent front screen 149 is illuminated by lights 50.

FIG. 5B shows a cutaway side view of housing 40. Disc 41 is alsoilluminated by white lights 50y and held at a steady level ofillumination. White lamp and retiector 51 illuminate the central portion`52 of screen 44. Lamp 51 is connected in parallel with white lamp 53which illuminates the outer portion 54 of screen 44. Portions 52 and 54are at the same level of illumination as white sector 43. Physical redlamp 55 illuminates the middle ring 56 of screen 44.

When disc 41 revolves, the front of housing 40 appears as is illustratedin the front view of FIG. 5C. Middle ring 56 appears a highly saturatedflashing red. Areas 52 and l54 appear flashing white. Screen 49 appearsa steady white. The speed of rotation of the disc 41 typically isapproximately three to twenty revolutions per second.

FIGS. 6A through 6C illustrate another form of signal light. In thiscase, housing 60 contains projectors 61, 62 and 63 along with motor 64to drive disc 65 which gives a Bidwell effect of a succession of imageson black translucent (light transmitting screen which appears black innormal ambient light when there is no light projected from behind)screen 66. Projectors 61, 62 and 63 contain steady physical white lightsources. Projector 61 has opaque slide 67 of FIG. 6B in it. This slidehas the word STOP in physical red translucent letters. Projector 62contains transparent slide 68 which has the word STOP in opaque blackletters on a translucent white background. Projector 63 illuminatesscreen 66 with white light by means of translucent slide 69. Disc 65 hasapertures and masks, i.e., an opaque shutter with slots therein whichtransmit or block the light from the three projectors.

FIG. 6C illustrates the three phases which appear on screen 66. First,disc `65 permits slides 67 and -68 to be projected superimposed so thatthe word STOP appears in physical red against a white background. Next,disc 65 permits slide 69 to be projected so that the entire screen 66appears white. Finally, disc 65 blocks all projected light and theentire screen 66 appears black. Disc 65 turns clockwise at about 5r.p.s. The above described repetition causes the word STOP to appearflashing in highly saturated red on screen 66.

Obviously in the illustration shown in FIG. 6 as well as in theillustration shown in FIG. 5, electronic switches are not required toturn the lights on and off since the disc With a Bidwell effect performsthis function. Therefore, incandescent lamps may be used rather than thegaseous lamps which were required in FIG. 4 because of the rapid on andoff fluctuation. Also rather than using disc 65 the means of FIG. 6could employ individual shutters in front of each projector. Theseshutters could be operated by electrical, mechanical or pneumatic meansin the proper sequence. While FIG. 6 illustrates a rear projectionmeans, front projection could also be employed. FIGS. 7A and 7Billustrate the use of drum 70, rather than a disc in connection withsignal light housing 71. Drum 70 is rotated by motor 72. Signal lighthousing 71 contains white lamp and reector 73 which back illuminateswhite translucent screen 74 with blue translucent letters HIT 75.Sectors 76 (shown layed flat in FIG. 7B) are 12 lters and masks on drum70.

FIG. 7B shows the light intensity cycle sequence created by l0 neutraldensity lters and 2 masks of sectors 76 on drum 70. The filtertransmission percentages are given for phases 1 and 3 through 11. Phases2 and 12 have opaque masks.

Drum 70 rotates at l0 r.p.s. giving the word HITS a saturated bluecolor. The subjective effect utilized here is the same one utilized inlamp 28B of FIG. 4F, and the filters and masks reproduce the voltagevariation for blue shown in FIG. 4G. This and other of the apparatus'illustrate how many of the color-blind can know the physical color of asignal or display because they see a subjective color the hue of whichmatches the physical color of the light.

FIGS. 8A through 8C illustrate the application of the combination ofsubjective and physical colors to an illuminated advertising billboard.The painted billboard has, in this example, black translucent (similarto screen 66 of FIG. 6A) screen 80 (cola can and liquid flowing fromcan) which normally appears blue and black and white because it is backilluminated by lights, illustrated in FIG. SB. Lights 84 illuminate theword BLUE and the crest of the waves with a physical blue color. Lights82 and 83 simultaneously illuminate the trough of the waves and the topbackground white. When lights 84 are out, lights S2 and 83 illuminatethe entire screen white. The word COLA is black at all times. Whenlights 82, 83 and `84 are off, translucent screen 80 appears black.

Likewise black translucent screen 85 normally appears red and Whitebecause lights 87 give a physical red outline to the fire; and light 86illuminates the central and surrounding portions of screen 85 White.When lights 87 are oli?, the entire area is illuminated White by light86. When lights 86 and `87 are off, physical red light 818 is turned onto illuminate the entire screen red. Then light 88 is turned 01T andphysical blue light 89 is turned on to illuminate the entire screenblue. The Words Fiery Thrist are black at all times.

FIG. 8C illustrates the sequence of 5 phases 'which screen 80 and 85 gothrough to create highly saturated color images. This sequence can beobtained by using switches similar to those drawn in FIG. 4D and voltagecycles as illustrated in FIG. 4E to turn on and otf lights, 82, 83, 84,86, `87, 88 and 89 at the proper times. Area 80 is shown as goingthrough black phase(s) which correspond to sector 1 of the disc in FIG.l. Area 85 is shown going through all blue and all read phases whichcorrespond to areas 10 and 11 of the disc illustrated in FIG. 1B. Areas80 and 85 need not be in phase or synchronized with each other so longas they each go through the proper sequences.

FIG. 9 illustrates another application for the combination of subjectiveand physical colors. Here command board 90 is being observed in abriefing room. Projectors 91 and 92 are projecting symbols 93 and 94 ofenemy and friendly missiles. Symbol 93 is in physical red color andsymbol 94 is in physical green c`olor. The position and movement ofsymbols 93 and 94 are being plotted by computer 95 which drivesprojectors 91 and 92.

On projector 91 is subjective color coding shutter mechanism 96 and onprojector 92 is subjective color coding shutter mechanism 97 which arealso driven by computer 95. Mechanism 96 modulates the light fromprojector 91 through the subjective red voltage cycle shown in FIG. 4G.Mechanism 97 modulates the light from projector 92 through the greenvoltage cycle shown in FIG. 4G. Images 93 and 94 can therefore be madeto appear highly saturated, which will cause them to stand out fromother physical color images on command board 90.

FIGS. A and 10B illustrate how subjective color can be added to physicalcolored motion picture film, physical colored television or other visualcommunication means. Illustrated here are four phases or frames whichcomprise one sequence of subjective color being added to a physicalcolor ilm strip or to physical color television. Each frame is dividedinto color creating area 98 and surround area 99. The colors in surroundarea 99 are identical in all frames. In color creating area 98 the firstframe shows stripes .100 of the flag in physical red; the second frameshows flag pole 101 in physical green; the third frame shows star 102 inphysical blue; and the fourth frame is opaque. In frames 1, 2 and 3 theoutline 103 of the ag is black, and the white stripes 104, eld 105 andbackground 106 are white. In this example, in area 98 this sequence isrepeated over and over 6 sequences per second for 24 frames per secondsound film projection. Or if the sequence is used with television it isrepeated 7.5 times per second for a frame television system.

FIG. 10B illustrates the picture as reproduced on the screen. The colorsin area 98 are now highly saturated because of the addition ofsubjective color to the physical color of the communication medium(these can be compared to the normally saturated physical colors in`area 99). This corresponds to FIG. l; however, rather than the blurcircles resulting in FIG. 1 there is a complex image reproduced in FIG.10B. The subjective color is added to the physical colored image only inarea 98 which has a flash or flicker; the balance of the raster remainssteady.

From the foregoing description, it is evident that the present inventionprovides methods and apparatus for obtaining highly saturated coloredlights and images. This invention is also applicable to radar, computerreadouts and other signaling, advertising and communication systems.

The present embodiments of this invention are to be considered in allrespects as illustrative and not restrictive.

What is claimed is:

1. A method of obtaining color stimuli by combining physical color withsubjective color stimuli comprising providing physical chromatic colorfrom light source means, and modulating light from said light sourcemeans in accordance with a subjective color stimuli producing code.

2. A method as in claim 1 wherein said light source means is a colorcathode ray tube,

and said physical color and said subjective color stimuli are combinedby modulating colored light from the phosphor of said cathode ray tubein accordance with said subjective color stimuli producing code.

3. A method as in claim 1 wherein lsaid light source means is a lampsource, and said physical color and said subjective color stimuli arecombined by modulating colored light from said lamp source in accordancewith said subjective color stimuli producing code.

4. A method as in claim 1 wherein said light source means is afluorescent color means,

and said physical color and said subjective color stimuli are combinedby modulating colored light from said uorescent color means inaccordance with said subjective color stimuli producing code.

5. A method as in claim 1 wherein said light source means is a lasersource, and said physical color and said subjective color stimuli arecombined by modulating colored light from said laser source inaccordance with said subjective color stimuli producing code.

6. A method as in claim 1 wherein said light source means is a colorreflecting surface of an element, and said physical color and saidsubjective color stimuli are combined by modulating light emanating fromsaid color reliecting surface in accordance with said subjective colorStimuli producing code.

7. A method as in claim 1 for obtaining mixed color stimuli wherein saidcolored light source means has a first hue and said subjective' colorcode produces a second different hue thereby resulting in a mixed colorstimuli of a third hue.

8. A method as in claim .1 for obtaining highly saturated color stimuliwherein said colored light source means has a hue substantially the sameas that produced by said subjective color stimuli producing code therebyresulting in a highly saturated color stimuli of substantially the samehue.

9. A method of obtaining color stimuli by combining physical color withsubjective color stimuli by modulating a physical chromatic color lightsource means in accordance with a complex subjective color stimuliproducing code, comprising a sequence of varying said physical colorlight source means in predetermined complex increments from off to onand back to off.

10. A method of producing highly saturated color stimuli on imagedisplay apparatus comprising selecting an area in an image to be highlysaturated, coding said area in accordance with a subjective colorstimuli producing code, and

exhibiting said coded area in physical chromatic color, said subjectivecolor stimuli producing code being that for producing subjective colorstimuli corresponding with the hue of said physical color.

11. A display apparatus for providing a subjective color stimuli andincluding display means having adjacent iirst and second portionswherein a highly saturated red color stimuli is produced by said secondportion, comprising a first illumination means for illuminating said rstportion,

a second illumination means for illuminating said second portion, saidfirst and second illumination means emanate white light,

switching means coupled with said first and second illumination meansfor turning on and ofic said first and second illumination means inmodulation sequences in accordance with a subjective color stimuliproducing code, and

a third illumination means which emanates physical red color light isdisposed for illuminating said second portion, all said illuminationmeans being turned on and off by said switching means in said modulationsequences, the intensity variations of each illumination means beingsubstantially as follows:

said first -illumination means being ofi during the first period of saidsequence and on during the second period of the sequence,

said second illumination means being off during the rst period of saidsequence and continuing off and then on during the second period of saidsequence, and

said third illumination means being off during the first period of saidsequence and on, and then off during the second period of said sequence.

12. A display apparatus for providing a subjective color stimuli andincluding display means having adjacent first and second portionswherein aihighly satu-s rated green color stimuli is produced by saidsecond por-v tion, comprising j a first illumination means forilluminatingsaidfirst portion,

a second illumination means for illuminating said second portion, rsaidfirst and second illumination means emanate white light,

switching means coupled. with said first and second illumination meansfor -turning on and off said first and second illumination means inmodulation sequences in accordance with a subjective color stimuliproducing code, and

a third illumination means which emanates physical green color light isdisposed for illuminating said second portion, all said illuminationmeans being turned on and off by said switching means in said modulationsequences, the intensity variations of each illumination means beingsubstantially as follows:

said first illumination means being off during the first period of saidsequence and on during the second period of the sequence,

said second illumination means being off during the first period of saidsequence, and then on, off, and on during the second period of saidsequence, and

said third illumination means being off during the first period of saidsequence, continuing ofi, then on, and then off during the second periodof said sequence.

13. A display apparatus for providing a subjective color stimuli andincluding display means having adjacent first and second portionswherein a highly saturated blue color stimuli is produced by said secondportion, comprising a first illumination means for illuminating saidfirst portion,

a second illumination means for illuminating said second portion, saidfirst and second illumination means emanate white light,

switching means coupled with said first and second illumination meansfor turning on and off said first and second illumination means inmodulation sequences in accordance with a subjective color stimuliproducing code, and

a third illumination means which emanates physical blue color light isdisposed for illuminating said second portion, all said illuminationmeans being turned on and off by said switching means in said modulationsequences, the intensity vibrations of each illumination means beingsubstantially as follows:

said first illumination means being off during the 'first period `ofsaid sequence and on during the second period of said sequence,

said second illumination means being off during the first period of saidsequence, on, and then off during the second period of said sequence,and

said third illumination means being off during the first period of saidsequence, continuing ofi and and then on during the second period ofsaid sequence.

14. A display apparatus for producing subjective color stimulicomprising light source means, and

means for modulating said light source means in accordance `with asubjective color stimuli producing code by repetitively varying theintensity of said light means in predetermined increments at least fromoff to full on, and back to olf, wherein physical chromatic color lightemanates from said light source means, and the varying of the intensityof said light source means occurs in a modulation sequence in accordancewith a code for a subjective color stimuli Whose perceived hue issimilar to the fhue ofthe physical color of said light source meansthereby resulting in a highly saturated color of a similar hue.

1S. A display apparatus for producing a subjective color stimulicomprising display means having adjacent first and second portions, afirst illumination means for illuminating said first portion, a secondillumination means for illuminating said second portion, shutter meansdisposed for modulating light emanating from said illumination means ina modulation sequence in accordance with a subjective color stimuliproducing code, and said second illumination means emanates a physicalchromatic color light which illuminates said second portion, and saidmodulation sequence is in accordance with a code for a subjective colorstimuli Whose perceived hue is similar t0 the hue of said physicalcolor. 16. A display apparatus for producing a subjective color stimulicomprising display means having adjacent first and second portions, f afirst illumination means for illuminating said first portion, a secondillumination means for illuminating said second portion, shutter meansdisposed for modulating light emanating from said illumination means ina modulation sequence in accordance with a subjective color stimuliproducing code, and said second illumination means emanates a physicalchromatic color light which illuminates said second portion, saidmodulation sequence is in accordance with a code for a subjective colorstimuli Whose perceived hue is dissimilar to the hue of said physicalcolor. 17. display apparatus for producing color stimuli comprisingfirst means for emanating physical chromatic color light, and modulatormeans for modulating said physical color light in accordance with asubjective color stimuli producing code. 18. display apparatus forproducing color stimuli comprising a display screen, a first whiteillumination means for illuminating said screen, a second chromaticcolored illumination means for illuminating said screen, and a modulatormeans for modulating light from said first and second illumination meansin accordance with a subjective color stimuli producing code. 19. Adisplay apparatus for producing a highly saturated color stimulicomprising a physical chromatic color light source means of a first hue,and means for modulating the light emanating from said light sourcemeans in accordance with a subjective color stimuli producing code forproducing subjective color of a similar hue. 20. A display apparatus forproducing mixed color stimuli comprising a physical chromatic colorlight source means of a first hue, and means for modulating the lightemanating from said light source means in accordance with a subjectivecolor stimuli producing code for producing subjective color of adifferent hue.

(References on following page) 15 16 References Cited ClearingHouse-CFSTI) I. Prs.: 37518; TF66-33946. Sheppard, J r., TemporalFactors in Subjective Colors, September 1966 PP 38-42 Cohen et a1. ThePrevost Fechner-Benham Sub ecl M-4770ARPA, M J d. Corporation Report Rarch tive Colors, Psych. Bul. 46(2), March 1949, pp. 97-136.

Frost, Generation of Subjective Colors in an Electro- 5 l luminescentDisplay, IEEE Intl Conv. Record, v01. 13, RONALD L' WIBERT PnmaryExammer Part 8, 1965, pp. 14-20. R. J. WEBSTER, Assistant ExaminerChuyev, Receiving Color on a Black and White Kiue- Us C1 X R scope, 22dAll Union Scientic Session. Devoted to radio day section on television(avail. from Commerce 10 l0-106521 13,2; 352-42; 356-473; 552-45

